Prime Minister John Key has said documents to back up his argument that New Zealand never got close to carrying out mass surveillance have been declassified, and he will release them to protect his reputation against damaging attacks from the journalist.

He has repeatedly said the GCSB has not collected mass data on New Zealanders and nor have New Zealand's Five Eyes partners done so to circumvent New Zealand law.

Speaking to reporters in Christchurch today, he rejected accusations he was releasing the documents for political gain.

"It's a bit rich though to say that it's expedient when here's a guy that's used hacked information presenting a case that's actually wrong, now he only saw one part of it and that's as I said a big problem, once you hack into something, you present the wrong picture don't you, because you know he might of been right if it had carried on all the way through but unfortunately for him he's completely and utterly wrong."

Mr Greenwald earlier told Nine to Noon an article from whistleblower Edward Snowden will show data on New Zealanders was collected by the Government Communications and Security Bureau in its role as a member of the Five Eyes network.

It talks about his first hand work at the US National Security Agency with large amounts of New Zealand metadata, provided by countries such as the US and the UK as well as the GCSB, he said.

"My source, Edward Snowden, who has never proven to have been anything but entirely accurate, whatever else you might think of him, is very definitive that large amounts of indiscriminate metadata have been contributed to the Five Eyes programme about New Zealanders," said Mr Greenwald. New Zealand, the US, the UK, Canada and Australia belong to the network.

Mr Greenwald plans to release other information on the GCSB's activities at an event hosted by Internet Party founder Kim Dotcom in Auckland tonight.

Key releasing documents to protect reputation

Speaking on Morning Report, Mr Key said Mr Greenwald's accusations about considering a surveillance programme had referred to a proposal about collecting information to prevent cyber attacks. The GCSB was working on the proposal but the idea was never put into action.

Mr Key said the proposal was well and truly killed by the time there was public debate about it.

"In the end you would have had to change the law, probably, to pass it. We did a lot of work on SIS as well, because in the end our view of the law there is it's not perfect, and there's been some changes."

Asked whether it was in the public interest for New Zealanders to know the GCSB was considering this programme, Mr Key said it was not, but he had no option but to release the information now.

"Greenwald's going to turn up tonight as part of a Dotcom sound and light show five days before an election trying to influence New Zealanders.

"He's made claims on television ... that are deliberately attempting to damage my reputation and tell New Zealanders that I'm doing something that I'm not and I've got no option but to protect myself."

Mr Key said he would release the documents to back his arguments, but only after Mr Greenwald had released his evidence.

But Green Party co-leader Russel Norman said the Prime Minister was behaving in a reprehensible manner by politicising the country's security and intelligence agencies.

Dr Norman said it was reckless for Mr Key to be releasing spy documents because it suited him.

"This kind of politicisation of the security services is extremely dangerous for a democracy, because the security services have all sorts of powers to gain access to information which is really dangerous to a democratic system, and that's why it's very important it's not politicised which John Key is now doing."

'Surveillance programme underway'

Mr Greenwald said the Prime Minister had continuously told the public New Zealand would never engage in mass surveillance and now has admitted for the first time that it was being actively considered.

"They did far more than merely consider it, they took active steps to implement it," he said.

"They were working with the NSA (US National Security Agency) on what the progress they were making was and they were simply waiting for enactment of the new law that they thought would give them whole new powers to be able to do this, at the very same time the Prime Minister was assuring the public that this new law would give them no powers."

Mr Greenwald told Morning Report he had NSA documents showing that the GCSB programme was underway; that "phase one" had been achieved and that "phase two" was waiting for a change to legislation to implement the programme.

The first phase was was about accessing the underwater internet cable which connects New Zealand to the rest of the world.

"Phase one entailed accessing that cable, tapping into it and then phase two would entail metadata probes - the sweeping up of large amounts of metadata indiscriminately in order to troll through it and analyse it and find out who New Zealanders are talking to."

The Government Communications Security Bureau and Related Legislation Amendment Bill was passed in August 2013. Under the bill the GCSB is able to assist the SIS, police and Defence Force in warranted interceptions of New Zealanders.

'PM changes tune'

Laila Harre. Photo: RNZ / Kim Baker Wilson

Internet Party leader Laila Harre said the 48 hours Mr Greenwald has been in the country Mr Key has dramatically changed his tune from previous assurances that the GCSB was not involved in mass surveillance.

"He has already admitted that the GCSB were at the very least developing a business case that would enable the indiscriminate collection of data."

Labour Party leader David Cunliffe said a Labour-led government would review the country's spying activities regardless of what Mr Greenwald reveals tonight.

He said Labour's proposed review would consider whether the country's spying activities are lawful, compatible with its values and whether there is enough oversight.

Mr Cunliffe said the Prime Minister should release documents on the spy agency as soon as possible but would not commit to releasing them himself if he was the next prime minister.

"Well I don't know what's in them so how can I make that decision. You go ask the Prime Minister," he said.